1261. Find Elements in a Contaminated Binary Tree

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1261. Find Elements in a Contaminated Binary Tree

Description

Given a binary tree with the following rules:

  • root.val == 0
  • If treeNode.val == x and treeNode.left != null, then treeNode.left.val == 2 * x + 1
  • If treeNode.val == x and treeNode.right != null, then treeNode.right.val == 2 * x + 2

Now the binary tree is contaminated, which means all treeNode.val have been changed to -1.

Implement the FindElements class:

  • FindElements(TreeNode* root) Initializes the object with a contaminated binary tree and recovers it.
  • bool find(int target) Returns true if the target value exists in the recovered binary tree.

Example 1:

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Input:
["FindElements","find","find"]
[[[-1,null,-1]],[1],[2]]

Output:
[null,false,true]

Explanation:
FindElements findElements = new FindElements([-1,null,-1]);
findElements.find(1); // return False
findElements.find(2); // return True

Example 2:

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Input:
["FindElements","find","find","find"]
[[[-1,-1,-1,-1,-1]],[1],[3],[5]]

Output:
[null,true,true,false]

Explanation:
FindElements findElements = new FindElements([-1,-1,-1,-1,-1]);
findElements.find(1); // return True
findElements.find(3); // return True
findElements.find(5); // return False

Example 3:

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Input:
["FindElements","find","find","find","find"]
[[[-1,null,-1,-1,null,-1]],[2],[3],[4],[5]]

Output:
[null,true,false,false,true]

Explanation:
FindElements findElements = new FindElements([-1,null,-1,-1,null,-1]);
findElements.find(2); // return True
findElements.find(3); // return False
findElements.find(4); // return False
findElements.find(5); // return True

Constraints:

  • TreeNode.val == -1
  • The height of the binary tree is less than or equal to 20
  • The total number of nodes is between [1, 10^4]
  • Total calls of find() is between [1, 10^4]
  • 0 <= target <= 10^6

Hints/Notes

  • N/A

Solution

Language: C++

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
 * right(right) {}
 * };
 */
class FindElements {
public:
    TreeNode* root_;
    set<int> nodes;

    FindElements(TreeNode* root) {
        if (!root) {
            root_ = nullptr;
        }
        root_ = root;
        traverse(root_, 0);
    }

    void traverse(TreeNode* node, int curVal) {
        if (!node) {
            return;
        }
        node->val = curVal;
        nodes.insert(curVal);
        traverse(node->left, curVal * 2 + 1);
        traverse(node->right, curVal * 2 + 2);
    }

    bool find(int target) { return nodes.contains(target); }
};

/**
 * Your FindElements object will be instantiated and called as such:
 * FindElements* obj = new FindElements(root);
 * bool param_1 = obj->find(target);
 */